Field of the Invention
Embodiments of the invention generally relate to optoelectronic semiconductor devices, such as photovoltaic devices including solar cells, and methods for fabricating such devices.
Description of the Related Art
The use of optoelectronic devices, such as photovoltaic devices and light emitting diodes (LEDs), is becoming more widespread as energy efficiency increases in importance. In a photovoltaic device such as a solar cell, the junction of a solar cell absorbs photons to produce electron-hole pairs, which are separated by the internal electric field of the junction to generate a voltage, thereby converting light energy to electric energy. The absorber layer of an ideal photovoltaic (PV) device would absorb all of the photons impinging on the PV device's front side facing the light source since the open circuit voltage (Voc) or short circuit current (Isc) is proportional to the light intensity. However, several loss mechanisms typically interfere with the PV device's absorber layer absorbing all of the light reaching the front side of the device. For example, some photons may pass through the absorber layer without affecting any electron-hole pairs and thus never contribute to generating electrical energy by the device. In other cases, the semiconductor layers of the PV device may be shiny and, therefore, may reflect a substantial portion of the impinging photons, preventing these photons from ever reaching the absorber layer.
Accordingly, there is a need for optoelectronic devices with increased efficiency and methods for fabricating such optoelectronic devices at reduced costs and greater flexibility when compared to conventional optoelectronic device fabrication.